Question 862401
Chris finishes 1/3 of the job per hour. Matt finishes 1/9 of the job per hour.<P>
The formula is time x rate = portion of the job completed.<P>
Matt works 4 hours, so he completes 4 * 1/9 = 4/9 of the job.<P>
Chris has to complete the job.  99 - 4/9 = 5/9 of the job remaining.<P>
time x rate = portion of the job completed<P>
t * 1/3 = 5/9<P>
t = 5/9 * 3/1 = 5/3 hours.